A well-known observation in the computing industry called Moore's Law states that the number of transistors on integrated circuits doubles approximately every two years, with a corresponding increase in processing speed. Lesser-known is Kryder's Law, first popularized by Mark Kryder, former chief technology officer for SEAGATE, which says that magnetic disk storage capacity increases at a faster rate than processor speed.
While disk storage capacity has been increasing at an exponential rate, disk throughput speed has increased only linearly. One approach to dealing with this disparity is the use of redundant arrays of inexpensive disks (RAID). In some RAID configurations, a file may be broken into chunks and stored across several devices in the storage array. Since the chunks that include the file can be written and subsequently read again in parallel, the RAID array provides the performance of a single, large-capacity, faster device.
Another factor that has not kept pace with the rate of increase in disk capacity is the mean time between failure (MTBF) for disk drives. Various RAID configurations address the potential for data loss due to disk failure by mirroring, data parity schemes, or both. Data on a failed disk in a RAID array can be rebuilt, sometimes even without shutting off the storage array when replacing the failed disk drive. But because disk capacity has grown so large, the process of rebuilding data on a failed disk can take hours, or even days. During the rebuilding process, performance and capacity of the storage array may be reduced.
In view of the above, the instant disclosure identifies a need for systems and methods for decreasing RAID rebuilding time.